PROJECT SUMMARY Cell-based therapy represents a promising strategy in regenerative medicine. However, live cells need to be carefully preserved and processed before usage. In addition, as ?live drugs?, cell transplantation carries certain immunogenicity and/or tumorigenicity risks. The development of cell-free and non-living therapeutics has the potential to revolutionize current regenerative medicine practice. Mounting lines of evidences indicate that adult stem cells exert their beneficial effects mainly through the secretion of pro-regenerative factors. Based on this, the PI Cheng Lab fabricated cell mimicking microparticles (CMMPs) by encapsulating stem cell-secreted factors in a biodegradable polymer block. Our previous studies demonstrated that those ?synthetic cells? carried similar secreted proteins and membranes as their parental cells did. In a mouse model of myocardial infarction (MI), intramyocardial injection of CMMPs led to preservation of viable myocardium and augmentation of cardiac functions similar to cell therapy. Despite the successful proof of concept, a big challenge is the effective delivery of those therapeutic microparticles to the heart. Cardiac patches have been tested to deliver therapeutic cells to the surface of the heart. One caveat is that there is a lack of patch-host communication due to poor integration of the cardiac patch with the host myocardium. The MPI Gu Lab is experienced in the fabrication of microneedle (MN) patches. Our previous studies indicated that MN patch can deliver therapeutics to the tissue effectively. The present R01 proposal represents a logic progression from our previous work while bringing new technologies. Here we will be developing and testing a new entity: a MN-CMMP cardiac patch formed by embedding CMMPs into biodegradable and biocompatible microneedle cardiac patches. In addition, our studies will extend from the previous rodent acute MI model to a chronic MI model in both small/large animals. The overarching hypothesis is that MN-CMMP can further improve the efficacy of CMMP therapy in rats and pigs with chronic heart injury. AIM 1: Fabricate MN-CMMP comprised of microneedle patch loaded with CMMPs; Determine in vitro potency of MN-CMMP in cultured cells. AIM 2: Determine the safety and efficacy of MN-CMMP therapy in rat model of chronic MI. AIM 3: Translate the findings into clinically-relevant porcine models of heart injury. Our study will form the foundation for an innovative and ?off the shelf? therapy based on secreted factors and myocardium matrix that can be standardized from donor stem cell lines and xenogenic cardiac tissues. The cell-free nature of our approach is more readily translatable to the clinic. Although this particular grant application targets the heart and cardiac stem cells, our approach represents a platform technology that can be applied to the creation of multiple types of synthetic stem cell and organ matrices for the repair of various other organs.